Arch Enemy
by salmon000001
Summary: The story of how Sherlock gained his arch enemy. A little language and S/J at the end if you squint.


_Woo! First new story in years. Written for a prompt: He's the most dangerous man in London, because he will break your heart one day. Sherlock loves Mycroft, but he is afraid that Mycroft might break his heart._

_Hope you enjoy it._

Contrary to how he usually acts around people, Sherlock does in fact love his brother. Anybody who has seen them together in this later part of his life would probably be surprised at this and even more surprised to learn that despite the way he acts, he actually likes Mycroft as well. Which has always been more important than love, at least in Sherlock's book.

His father was always very detached when they were growing up, oh he was always courteous to Sherlock and Mycroft when he was there (which was almost never), but they never played games together or read together or did any of the things fathers generally do with their sons. And Sherlock does love him, after all it's his father and it's a preprogramed trait that the majority of people have barring some traumatic incident when they are young. However Sherlock can safely say that he does not know enough about his father's personality to decide whether to like him or not.

And Mummy….Sherlock, even now, does not like to think too much about Mummy.

Mycroft was his constant companion as a child. They were both home schooled and very much isolated in their own little world. At least Sherlock was. Mycroft was six years his senior and involved in as many out of school clubs as he could manage. Beavers (then Cubs and Scouts when he was old enough), a plethora of music clubs (he played the oboe, averagely well objectively, though it was mediocre in compassion to Sherlock and his violin), a Saturday morning set of classes on 'varied academic topics' and Sherlock even remembered him joining a sports team for a brief period of time (although that one didn't go so well).

Sherlock on the other hand rebelled against that sort of ordinariness and when his parents signed him up against his wishes for Beavers it did not go well. He should at least give them a try, his mother cajoled, you might find you like them, it would be good for you to have some friends your own age she said. However even at 6, his scathing remarks insulted almost everybody there and even made one boy cry. At the end of the session the leaders of the club quietly mentioned to his parents that maybe it would be better if he didn't come again. He didn't go again.

But despite their differences, Mycroft and Sherlock had so much in common that Sherlock's introverted ways and Mycroft's outgoing ways didn't seem to matter. Mainly it was their intelligence that helped to keep them so close. It was very relaxing for Sherlock to be able to have an interesting conversation from someone who wasn't an adult. Because the adults never forgot they were talking to a child, and while they had decided it was a good idea not to dumb things down with him after that incident with the screwdriver, he was still only a boy and a young one at that.

Sherlock and Mycroft would spend lazy afternoons talking about Nietzsche and chemistry and reading. They would spend nights playing chess or whatever other games Sherlock or Mycroft could cook up. It was brilliant. Of course they also got up to plenty of mischief and did the things that all brothers do. They wrestled and fought and yelled. They ignored each other for hours when they were angry. But it was never serious and being young they usually forgot most of it after a couple of days. They were still children, albeit very smart and well aware ones.

But then Mycroft had to leave for university. He went earlier than most at 16; he was definitely capable of it and had been for years. Sherlock was capable of it. But when he had pleaded with his mother she had just smiled at him and shook her head. He thought that was particularly unfair.

At this time Sherlock had not quite finished working on his 'science of deduction' as he called it. He was capable enough but he still needed more data, the data that would enable him to make big leaps that nobody else would; splash patterns, different types of mud, how certain chemicals reacted together (not the boring types he would find in his text books). He was a decent way into his study, but it was no way near complete. He was 10 at the time.

So while Sherlock was beginning to draw together the skills that would make him so indispensable to the police later in life, he was no way near complete in them. Which is why he did not realise Mycroft was leaving until he saw Mycroft lugging several suitcases upstairs. Then it all came together. The small signs of deceit he had been noticing for the last few weeks but had said nothing after all, it was Mycroft; he didn't need to worry about Mycroft.

He stormed into Mycroft's room just as he put the suitcases on his bed. He was angry, very angry and just a bit hurt.

"You're leaving." Sherlock said and Mycroft stilled with his back to Sherlock. He slowly turned around. Sherlock didn't need to say where, they both knew.

"Yes," he said plainly.

"Were you going to tell me?" Sherlock asked. He tried to keep his voice calm.

"Of course. You would have noticed my absence; it would be ridiculous for me not to tell you," Mycroft said, but he did not meet Sherlock's eyes.

"When? When you were actually walking out the door!"

"I..." Mycroft's voice trailed off.

"Why didn't you tell me?" Sherlock stepped slightly closer to his brother. Mycroft had gone through a growth spurt at 13 and Sherlock only came up to the bottom of shoulders but none the less they were equals. Or at least Sherlock had believed they were.

"I just..." Mycroft broke off and started again. "I wanted to...but it was never the right time."

"Never the right time," Sherlock stepped back slightly and brought the anger to the front again. "Right."

"It's all new for me Sherlock, I don't know what I'm doing and I wanted to make sure it was all actually happening before I told you. I knew you weren't going to like it, I was trying to make it easier on you." He said. And from the look on Mycroft's face, Sherlock knew he was telling the truth. His eyebrows were drawn in a worried line and he ran his hand through his hair. Mycroft did care a lot about Sherlock. But Sherlock had been hurt, by one of very few people he had trusted at all. The one person, who while not like him, had truly understood him in the way Mummy couldn't, although she tried her best. Who wasn't boring. So it was out of hurt and anger that the next words came out of his mouth.

"Who said I wasn't going to be happy?" Sherlock challenged. Mycroft looked worried.

"Why should I care? Why should I give a crap?" Sherlock said. He held the defiant look on his face. He wasn't going to admit weakness to Mycroft again. He was hurt, but he wouldn't let it show. It was his pride; he should have known, he should have figured it out sooner.

"Sherlock..." Mycroft pleaded and the look on his face made Sherlock want to give up this facade and hug his brother. But he stuck his jaw out before and held the same expression on his face. His drama tutor had always said he was a good actor.

When Sherlock said nothing again, still glaring, Mycroft sighed and then schooled his features into a similar manner.

"Fine, please get out of my room then Sherlock."

Sherlock stood there, still scowling and crossed his arms.

"I need to pack and unless you want to help I have a lot to do in this short space of time," he said turning his back to Sherlock.

Sherlock glowered for a few seconds and Mycroft's back and then stalked out of the bedroom and back into his own room. His body shook slightly as a tear rolled down his cheek, but he made no sound. And for the first time, and what young Sherlock also swore would be the last, he cried over another person.

After than moment things never got better between them. Mycroft would come back for Christmas and Easter and the summer, but things always stayed cold between them. In the first year after their argument Sherlock came close to caving twice; going to have a serious talk with Mycroft and asking for his brother back. And although Sherlock did not know it, Mycroft also came close, 3 times. But it never happened. A combination of pride and circumstance.

And as the time went on, Sherlock convinced himself he didn't miss it all that much. And Mycroft was always busy, with projects and papers at first and then his work in the government and Sherlock tried to put it out of his mind. He spent almost every moment not with his tutors or his parents alone and working.

When he was 14, his parents took him to a psychiatrist. He had become too engrossed in his work, specialising in crime and death, apparently that wasn't healthy. He mouth had also developed a horrible habit of bypassing his brain when he was around Mummy. Whenever he spoke it seemed to come out in the form of insults and terrible things which should never have been said and couldn't have been further from the truth. As soon as they came out of his mouth he always wanted to take them back, but annoyingly that was when he would clam up and not be able to think of a word to say. She cared about him and Sherlock wasn't going to let anyone care. He feared he would start to care back and then be in the same position he'd started in. Vulnerable, and able to be hurt.

The sessions with the psychiatrist were pointless. He knew the material better than the woman across from him and he knew more about her from her clothes and office than she ever did about him, despite the fact she had his parent's writings and his file. Sherlock could act out all of the conditions she had described in her large textbooks on her bookshelf, he knew the symptoms after all and they were easy enough to portray. He could have acted perfectly normal and she would have been none the wiser, however to him this was an opportunity, and after some consideration Sherlock had decided what he wanted to be diagnosed as. Sociopath.

Sociopathy was perfect. It was an extremely vague diagnosis and after that his parents (his mother) stopped what little they had been trying to do to get him to connect with people. It was perfect. It was a valid excuse for his insults and disconnection from people. He felt a vague sense of disquiet at the look on his mother's face when the idiotic woman told her but it really was the perfect solution. And he didn't care about Mummy, he reminded himself, though the lump in his throat took some time to go away.

Mycroft had known what Sherlock had done of course. When he had come home and Mummy had told him the diagnosis over the dining room table (Father had been away of course) he had given Sherlock a look, but never mentioned it.

Mummy had died when Sherlock was 15 years old. Heart problems.

Sherlock and Mycroft were never close again and as the years went on they became more and more antagonistic. Sherlock dropped sharp barbs at Mycroft whenever he could, to him it was protection. Mycroft had broken his heart and Sherlock would be damned if he let it happen again by anyone.

He went to Uni and made 'friends,' mainly for research. There was nothing like watching psychology put into practice and he was in a unique position to do it; being so young he would fit right in. But he always kept himself apart, dropping remarks that were offensive enough to stop them from getting too close but not enough to drive them away. He almost made an art out of it.

And then after many years and many trials and tribulations, there is John. And John is brilliant and amazing and maybe it is just enough to start wearing down his barriers again. And the funny thing is, Sherlock doesn't seem to mind.

But even with that, Sherlock still finds he can never seem to let down the barriers he put up to protect himself from Mycroft. Because they've been there since he was 10 and Sherlock knows that if he ever let them down again, started treating Mycroft the way he really feels it will just leave him open. Vulnerable. To get hurt again. And despite all the years of detachment and the way Sherlock has tried to remove himself, Mycroft persists. As if he's hoping one day Sherlock will give in and they can be best friends the way they used to be. And that is why Mycroft will always be Sherlock's arch enemy; he is one of the most dangerous people to Sherlock. Because he is one of only two people alive who still has the ability to break Sherlock Holmes heart.


End file.
